DE 3630822 C2 (Bridgestone) describes an arm pivotable about precisely one axis for an industrial robot. The arm is attached to a rotatably mounted belt pulley which is encompassed by a cable, a so-called pneumatic muscle being situated at both ends leading away from the belt pulley. A pneumatic muscle is made up of a tube-like center portion and two plate-like end pieces, at least one of which is provided with an air passage. When the tube-like center portion is inflated, its circumference is expanded and its length is reduced. This reduction in length can result from overcoming an external tensile force. When in the use case corresponding to DE 3630822 a pneumatic muscle is tightened, the arm is pivoted in a rotational direction; when this pneumatic muscle is released and the second pneumatic muscle is tightened, the arm is pivoted in the opposite direction. The arm is “touch-capable” in the sense that when an external force is applied, it yields elastically on its own accord with a soft characteristic, it being possible to infer the magnitude of the external force using position sensors and taking into consideration the pressure present in the pneumatic muscles. The described arm for industrial robots has not gained acceptance. Since the elastic yield is uncontrolled in this case, preference has been given to stiffer drive principles using, for example, electric motors or hydraulic cylinders and, if necessary, a “soft grip” has been implemented using separate gripping pieces.
U.S. Pat. No. 4,984,568 describes a robot arm used for back massage driven by a plurality of reciprocally pivotable hydraulic cylinders. It is affixed to the side frame piece of a bed frame, projects over the surface of the bed, and exerts pressure on the back of a person lying in a prone position on the bed. The robot arm can be controlled by the person lying on the bed by using a control unit. Massage robots of this type have a number of disadvantages. Hydraulic systems are costly, heavy, often disseminate an odor of hydraulic oil, and entail the risk of contamination by escaping hydraulic fluid. They are also dangerous as massage robots because an error in the hydraulic system can very rapidly cause dangerously high forces to be applied to the person being treated.
DE 195 24 666 C1 describes a massage robot which is also mounted on the side of a bed. The tool holder which is movable in three spatial coordinates via linear drives can hold various massage devices and thus act upon the person to be massaged. A number of programs are available for the controller. The action on the person is force-regulated. Pneumatic cylinders or electric motors are provided for the drives. To rule out dangers for the person to be massaged in the event of errors in the controller, predetermined breaking points are provided in the system which break if allowable forces are exceeded.
Massage robots of a very similar design are also described in U.S. Pat. No. 5,083,552 and US 2001/0014781 A1. When controlled suitably, these massage robots can provide an excellent massage. However, all of them have a very high purchase price, require a large amount of space, and have a menacing appearance. In addition, they are very prone to damage with regard to a number of forces which can occur when moved by persons in connection with the massage due to linear guides arranged in a cascade-like manner.
DE 101 39 807 A1 describes a robot arm for industrial applications built up from a plurality of interlinked pivotable levers. The joint between two levers is designed in a manner which is of particular advantage. The drive elements for the individual levers are electronically, hydraulically, or pneumatically operated lifting rod units situated directly on the levers. It is disadvantageous that these drive elements are relatively heavy, space-consuming, and costly.
BR 9303695 A describes a robot arm built up from a plurality of pivotable levers interlinked with one another, each of the pivoted levers being made up of a pivotable piece based on a support and two pneumatic muscles, the base and pivotable piece of one pivoted lever being affixed to opposite ends of the support, the pivotable piece being rotatably supported in relation to the support on an axis lying normally to it, the two pneumatic muscles extending between the base and the pivotable piece and engaging the pivotable piece on different sides of the pivot axis and the pivotable piece of a lever being rigidly connected to the base of the second lever. Despite the simple and robust structure, this design has so far not gained acceptance, presumably because an excessively large source of inaccuracies and hazards is seen in the somewhat difficult activation of the pneumatic muscle.
WO 2003080297 A1 describes the reproduction of a human hand and a human arm using interlinked, reciprocally pivotable pieces whose motion relative to one another is driven by pneumatic muscles, which act on the individual parts to be moved via cables whose function is similar to those of human tendons. The advantage of pneumatic muscles is seen in that they require less space compared with other driving means. However, the design according to WO 2003080297 A1 is nonetheless so complex that it inevitably results in excessively high costs and thus can hardly be used in an appreciable scope.
U.S. Pat. No. 5,417,643 and DE 299 22 651 U1 describe a chair equipped with a multi-element arm rest designed as a therapy device for the passive mobilization of persons. The individual elements are attached so as to be movably guided in relation to one another. Controllable drives operate between the individual elements. The patient sitting down on the chair places one arm on the armrest. According to a control program, the armrest is then moved and the patient's arm with it. There is no mention in the DE publication of what happens if the controlled movements of the armrest vary from the patient's possibilities for movement and thus could cause pain or even injury to the patient. According to the U.S. publication, a rapid cut-off is provided for this case. A disadvantage in this is that already dangerously high forces may have impacted the patient when this cut-off takes effect and the treatment is thus stopped.
According to EP 1 609 451 A1, a device for passive physical therapy is described which is made up of rigid, shell-like parts which are worn by the patient that are similar to pieces of a knight's armor and are connected to one another by joints. Pneumatic muscles act as controllable actuators between individual shell pieces moved in relation to one another. Nothing is said concerning the type of activation of the actuators. The design made up of shell-like pieces makes the device rather heavy and the process of putting it on and taking it off is somewhat laborious.
US 2003/0223844 A1 also describes a device made up of a plurality of rigid, shell-like elements worn by a person that are similar to the pieces of a knight's armor and are connected with one another by joints. The device is used for controlling a remote robot situated in space, for example. Elastically pretensioned Bowden cables assist in lifting individual elements against the force of gravity and are also used to measure the position of individual elements in relation to one another. As a function of the measuring result, a remote robot is moved. In an advantageous refinement, controlled forces are also exerted between the individual shells of the device as a function of forces acting on the robot.
Accordingly, it would be desirable to provide a robot arm which may be used in a large number of private households, in industry, and in medical technology. For reasons of cost, robustness, weight, and space, a design corresponding to BR 9303695 having pneumatic muscles as drive elements may be considered. In contrast, primarily the safety may be increased so that the robot arm does not damage anything by high forces or shocks at high speed and no one is injured, and the robot arm may be more simple to operate and usable for a larger number of different applications. In particular, the robot arm may also be usable as a therapy device for the passive and active mobilization of human limbs.